Food bars have been known and available for some time. They vary in composition, some having a marshmallow base and others, originally introduced as health food bars, are comprised of grain(s), nuts, dried fruit, sweeteners and other ingredients. In the latter, the dried ingredients are mixed with a binder, such as sugar syrup, shortening or fondant (which is sometimes a cooked syrup but is used herein to refer to a mixture prior to cooking), compressed into bars, and then cut to the desired length. Depending on the bars' composition, they may be mixed, formed, and/or baked prior to packaging and sale.
The addition of glycerine to food, as taught by Berg in U.S. Pat. No. 2,437,150, has resulted in better mold release and bonding strength of food bars. Glycerine and other polyhydric alcohols are known to also effect the shelf-life and texture of food bars. In U.S. Pat. No. 4,451,488, Cook et al. used polyhydric alcohols such as glycerine to increase the shelf life of food bars by decreasing the water activity (A.sub.w) but at the same time retaining good flavor characteristics and improved soft texture.
In recent years, the shelf-life of food has been extended through the use of a new technology which utilizes the concept of an intermediate-moisture food product. As is known, high levels of moisture in food generally promote the microbiological spoiling and growth of organisms such as yeast, molds and bacteria. Stabilization of food products has traditionally been effected through the use of inherent properties of food, such as the naturally high acid content that occurs in tomato sauces and the like; sterilization of the food followed by hermetic sealing; drying the food to moisture levels less than 10%; or freezing the product. Each of these methods has known drawbacks.
The intermediate-moisture foods rely on the reduction of the availability of water in the food to prevent microbial growth and lengthen shelf life. Such availability of water in the food is commonly termed water activity (A.sub.w). In general, a low A.sub.w, less than 0.90, indicates the existence of an environment in which most bacteria will generally not grow.
The A.sub.w of the food, or the partial vapor pressure of the water at the temperature of the food, can be readily determined by placing the sample in a sealed container and, upon reaching equilibrium, determining the relative humidity in the head space.
U.S. Pat. No. 3,202,514 to Burgess et al., which discloses an intermediate-moisture pet food, was the first to demonstrate the principle of extending the shelf-life of a food by controlling or altering the A.sub.w. Burgess et al. shows how the A.sub.w of a food product can be maintained at a low level by a high sugar content. U.S. Pat. No. 4,146,652 to Kahn et al. discloses the substitution of polyhydric alcohols such as glycerine and sorbitol for sucrose. U.S. Pat. No. 4,451,488 to Cook et al. incorporates this knowledge into the production of soft and chewy food bars.